The function duplicated identifies elements of a data
structure that are duplicated:

> x <- c(1, 1, 1, 2, 2, 2, 3, 3, 3)
> duplicated(x)

[1] FALSE TRUE TRUE FALSE TRUE TRUE FALSE TRUE TRUE

> x <- x[!duplicated(x)]
> x

[1] 1 2 3

This is a simple example, but works just as well to remove duplicated
rows from a matrix or data frame.

For whatever reason, suppose we have loaded the audit dataset into
Rattle and want to remove duplicated hours, keeping just the first
one of each. This process is performed external to Rattle and we
need to have Rattle reset its view of the data, through a click of
the Execute button, with the resulting smaller dataset as
shown in Figure 23.11.

> crs$dataset <- crs$dataset[!duplicated(crs$dataset$Hours),]

Figure 23.11:
The dataset has been modified
externally to remove specific rows and then the Execute button
clicked so that Rattle will notice the changes.